Ive had my fleets stuck on the edge of the screen to. damn annoying when u are trying to glass a planet and have to manually do the first few movements so the ai can take over
although as Marty pointed out, if u dont want the enemy to reach u its not a bug, it becomes a useful feature...
It isn't a great problem in tactical combat (you can always maneuver to "free" the AI ships), but once I had my fleet locked up on the map border in a PBeM game...